The present invention relates to a doctor blade for an ink unit of a rotary printing press. The doctor blade is at least partially coated with a substance of low surface energy.
It is well known to apply ink to rollers and to subsequently strip excess ink off the roller, for example the screen roller of a rotary printing press, by means of a doctor blade. Ink can collect, during operation of the screen roller, on a side of the doctor blade facing away from the ink duct. This ink collection is a problem particularly in connection with inks of high viscosity.
U.S. Pat. No. 4,070,964 discloses a doctor blade coated with Teflon for reducing the friction between the doctor blade and the screen roller.
NL-A-9300810 describes a doctor blade coated with Teflon.
The object of the present invention is directed to creating a doctor blade for rotary printing presses.
In accordance with the present invention, this object is attained by providing a doctor blade for a rotary printing press in which the doctor blade is at least partially coated with a substance having low surface energy. The doctor blade can be partially or completely coated on one or both sides over a part of its length or its entire length.
The advantages which can be achieved by means of the present invention in particular rest in that interfering ink accumulations are prevented on a side, typically the outside, of the doctor blade, which side faces away from the interior of the ink duct, i.e. the side of the doctor blade facing the ink metering roller. The smallest xe2x80x9cink dropletsxe2x80x9d leave the exterior of the doctor blade. No increased, interfering ink deposits can occur can create undesired fluctuations in the ink density on the print carriers such as, for example, a sheet or a web.